Origin and evolution of pituitary hormones : identification of hormone genes in an agnathans

本研究旨在通过对七鳃鳗的脑、垂体激素和受体的鉴定，了解脊椎动物生殖、生长和适应内分泌系统的起源和进化。垂体激素(1)我们从海七鳃鳗的垂体中鉴定出一个促性腺激素(GTH) β亚基，与促卵泡激素(FSH) β和促黄体生成素(LH) β亚基具有中间序列相似性。产gth细胞位于垂体远端近部的腹侧半部。七鳃鳗促性腺激素（GnRH）刺激GTHβ亚基mRNA。结果表明，七鳃鳗具有一个单一的GTH基因。我们假设一个单一的GTH基因出现在agnathan菌株中，因此FSH和LH可能出现在颌口。(2)测定了七鳃鳗GTHβ亚基、生长激素（GH）、促生皮素原（POC）和促黑素原（POM）基因的结构。(3)我们发现袋头七鳃鳗和短头七鳃鳗中POC和POM基因的含量高于海鳃七鳃鳗。这些发现表明，产生这两个基因的重复事件可能发生在现存的三只七鳃鳗的共同祖先身上。糖蛋白激素受体。我们从海七鳃鳗中鉴定出两种糖蛋白激素受体cdna：一种是位于性腺的gth样受体，另一种是位于甲状腺组织的tsh样受体。这有力地表明GTH和TSH也存在于agnathans中。脑激素(1)我们从七鳃鳗脑中鉴定出两种催乳素释放肽（RFa-A和B）的同源物。RFa免疫反应细胞不仅存在于下丘脑，还存在于垂体中间部。RFa-A和B均抑制垂体GH和POM mrna的表达。(2)从三科八种七鳃鳗中克隆了GnRH-III cdna。GnRH-III的序列可以分为三组，支持目前在家族水平上的七鳃鳗谱系的观点。少

This study aimed to understand the origin and evolution of endocrine systems of reproduction, growth and adaptation in vertebrates based on the identification of brain and pituitary hormones and receptor in an agnathans, lampreys.1.Pituitary hormones(1)We identified a gonadotropin (GTH) β subunit from the sea lamprey pituitary, showing intermediate sequence similarity to both follicle-stimulating hormone (FSH) β and luteinizing hormone (LH) β subunits. The GTH-producing cells were located in the ventral half of the proximal pars distalis of the pituitary. GTHβ subunit mRNA was stimulated by lamprey gonadotropin-stimulating hormones (GnRH). The results indicate that lamprey has a single GTH gene. We hypothesized that a single GTH gene occurred in a strain of agnathan, hence FSH and LH may have appeared in gnathostomes.(2)We determined the structures of GTHβ subunit, growth hormone (GH), proopiocortin (POC) and proopiomelanotropin (POM) genes in sea lamprey.(3)We demonstrated the presenc … More e of POC and POM genes in the pouched and short-headed lampreys, as in the sea lamprey. These findings suggest that the duplication event which generated the two genes may have occurred in a common ancestor of the three extant lampreys.2.Glycoprotein hormone receptor.We identified two kinds of glycoprotein hormone receptor cDNAs from sea lamprey : one is a GTH-like receptor located in the gonad and the other is a TSH-like receptor located in the thyroid tissue. These strongly suggest that GTH and TSH also exist in agnathans3.Brain hormones(1)We identified two homologues of prolactin-releasing peptide (RFa-A and B) from the sea lamprey brain. RFa immunoreactive cells were detected not only in the hypothalamus but also in the pars intermedia of the pituitary. Both RFa-A and B inhibited the expression of GH and POM mRNAs in the pituitary.(2)We cloned GnRH-III cDNAs from eight species of lamprey representing the three families of Petromyzoniformes. The sequences of GnRH-III can be divided into three groups supporting the current view of the lamprey lineage at the family level. Less